Property owners near universities were also making money with cabins.
"Quite a lot of people rent them out to students. They've got a cabin the backyard and then they'll get a student boarder."
When the students left, the cabin could be returned.
In Mt Roskill, Jenny Page's adult son was using a cabin. "Until we convert part of the garage into a sleepout, we've got a cabin on-site for him."
King said the cabins were fully insulated and equipped with power points and carpet.
The first RoomMate franchise was created in 2004. Hire in central or west Auckland started from $55 per week for a minimum six-month term. In Hamilton and Taranaki, it was $50 per week. In Manawatu it was $49.50.
King said councils rarely if ever had problems with cabins, because cabins were transportable, under 10 square metres and didn't have plumbing.
"You do still have to work with the height-to-boundary ratios, if you're too close to the edge of your section. Generally the council doesn't worry about that but if people don't get along with their neighbours, their neighbours can dob them in."